The Southern Subpolar Region is here taken to be the area between the Antarctic Divergence and Subtropical Convergence. This region is often referred to as the Subantarctic, but that name refers to that part of the region south of the Antarctic Convergence, which has colder summers and a complete lack of arboreal vegetation (Øvstedal & Lewis Smith 2001). As trees are present on some of the areas under consideration they should not be considered "Subantarctic" and so the term "Southern Subpolar" is preferred.

The U.S. National Park project contains over 29,000 records of documented occurrences of lichens in units of the U. S. National Park System. The records were obtained from the scientific literature, National Park Service reports, and the University of Minnesota Herbarium. Unpublished herbarium records from other herbaria are not included because they cannot be cited. Over 511 references reporting almost 2,550 lichen species from 151 park units are included. Only parks with reported lichens are included in the database. We have been unable to locate lichen references for other parks in the National Park system. Visit NPLichen: A Database of Lichens in the U.S. National Parks for more information on the project. All lichen names were standardized to Version 13 (2008) of Esslinger's Checklist of North American Lichens. This database was developed jointly by James P. Bennett, U. S. Geological Survey and University of Wisconsin, Madison, WI and Clifford M. Wetmore, University of Minnesota, St. Paul, MN. Funding for this database was provided by the U. S. Geological Survey, Madison, WI and the Great Lakes Network Office, National Park Service, Ashland, WI.